Many types of machines, apparatus and structural installations incorporate universal joints to non-rigidly connect together two adjacent objects when it is desired, or necessary, to have one or both of the objects pivot with respect to the other object, or to a third object. Such pivotal action is often involved even though there is no axial rotation as in a drive shaft.
At times a fluid conduit must extend from or between, and be secured to, objects connected together by a universal joint. Since the objects pivot with respect to one another at the universal joint, it is essential that the conduit include a non-rigid yieldable section at, or in the vicinity of, the universal joint which will not significantly interfere with the pivoting action between the objects.
There is much present interest in fluid conduit universal joint by-pass systems by oil companies engaged in offshore exploration, development and production. This is because such endeavors often require the utilization of a deep water offshore buoyant column or tower pivotally secured in place along its length by a universal joint. Oil or gas lines or conduits desirably run along the sea floor and then up the column to the column top. From the column top, oil or gas lines extend to a ship or structure moored to the column. The mechanism used to moor the ship or structure can include a universal joint at the column top so that the ship or structure is free to pitch and roll relative to the column. Since a fluid conduit must often extend from the column top to the ship or structure, it is necessary that the fluid conduit include a means by which fluid can be conveyed from a conduit on the column past the universal joint to a conduit on a mooring boom or yoke or to the ship or structure themselves.
Reid U.S. Pat. No. 4,010,500 discloses the use of a cardan type universal joint at the top and bottom of an offshore mooring column. The patent also discloses fluid coupling of a pipe from one side of the cardan joint to the other side by passing a conduit or pipe elbow through hollow pins of the cardan joint positioned 90.degree. from each other. Conduit or pipe sections communicate with each end of the elbow through suitable fluid swivels so that pivotal movement of the column to the base, or the ship mooring yoke to the column, is unrestrained yet a fluid tight coupling between conduit sections is achieved.
Because of the 90.degree. bend which the elbow must make inside of the cardan joint disclosed in the Reid U.S. Pat. No. 4,010,500, the joint must at times be sized larger than what is necessary to carry the axial, torsional and shear loads. Also, the sharp curve of the elbow internal of the cardan joint can restrict the pipe size which can be used and the sharp curve can prevent passage of a pig through the elbow, thereby making it impossible to clean the elbow without disassembly of the pipes. Furthermore, the Reid patent system is limited to conducting two flow lines or pipes from one side to the other side of the cardan joint.